I got an event Shaymin, and I want to know what moves to teach it. I'm going to use it an all-around type of pokemon.
BEdit* By all-around, I mean a pokemon that can attack and defend. All I need is a moveset. Its nature is serious.

Can you expand what you mean by "all around poke"? Also what nature/IV spread did you get?

Not to rian on anyone's parade here, but i find shaymin to naturally be a simply bidoof when it comes to power.
its learned moves are nothing to give a second look at, and it can't be breeded for better ones, though you cna slavage something, it won't come out very good in the long run.(this is all my opinion of course, but i'd honestly like to see a useful shaymin)

For the defensive part go for a sub leech seed seeing how shaymin has the ability to put up 101 Hp Subs, as for the offensive part go for seed flare and Hidden Power either Fire or something else that can handle several common types.

Lol, no. Shaymin outclasses Bibarel in every stat easily, and gets very nice moves in Pt from the tutors and sky fourme.

For a moveset on the land fourme I'd say, barring Hidden power and 101subs (unless you got one with a 31IV in hp)

-Rest (sleep removed via natural cure)
-Seed Flare
-Earth power
-Air Slash/leech seed/Sub

well, you have a point, i can see making shaymin more of a wall than anything, or an annoyer at best.
it just doesn't have the movesets to make it a worthwhile attacker...

In PBR I use a worry seed sceptile to help regigigas
but I have a fast Shaymin I haven't figured out if sky form shaymin is on PBR if so I'll use it to worry seed regigigas.

I think it should have a similar moveset to Rotom's, Confuse Ray, Double Team, Shock Wave, and Hydro Pump. Double Team and/or COnfuse Ray is a must-have, and it's signature move as well as a good move of a different type. I'm a dragon collector, so I don't really use Grass-type pokemon much, so I hope that helps.

@ Leftovers
EV: Spec. Attack and Defense?
Energy Ball
Substitute
Leech Seed
Some sort of attacking move that ain't grass

Being one of those "cute event" Pokemon, Shaymin's got base 100 stat in all stats. That makes it pretty difficult to figure out its potential, since usually a Pokemon's potential is easily noticed by its stats (Alakazam's high Spec. Attack makes it obvious it's a sweeper). But the advantage is it can become anything: mixed sweeper, tank, wall, sub-seeder, anything! THis set is like a Spec. Attack Breloom, just without Spore. Shaymin's only attack that induces sleep is GrassWhistle, which only has 55 accuracy (although those freakin' NPC always hit with it... Barry ) ANyway, you can use GrassWhistle if you think you are lucky. If you're using Skymin... well the set is obvious. Flinch hacks and Seed Flare is all you need.

Good luck soldier! (God i should make that my siggy)